POSSIBLE FACTORS INFLUENCING VERTEBRATE SEX-RATIOS - AN INTRODUCTORY OVERVIEW

Sex ratio theory is one of the more developed areas of evolutionary ec ology, yet adaptive explanations for sex ratio variation among vertebr ates are still the subject of much debate and uncertainty, partly beca use it can be difficult to infer process from pattern and adaptive and non-adaptive explanations may be confounding. In this introductory ov erview, I consider factors which may influence vertebrate sex ratios. I first consider 'theoretical factors', i.e. the adaptive value of the control of offspring sex ratio to parents. I then examine 'empirical factors' which influence parental ability to control offspring sex rat io, focusing on potential constraints imposed by sex determination mec hanisms. Finally, I outline some of the evidence for the influence of these factors on sex ratios. (C) 1997 Elsevier Science B.V.